Because Navesink and Robbins Reef Lighthouses aided in marking the nation’s busiest port, the federal government used both for several successful technological experiments that significantly improved maritime safety. Throughout history, the purpose of a lighthouse’s light has been to provide mariners with a fixed point of reference to guide them through waters at night or during bad weather when the shore or an offshore hazard cannot be seen clearly. Thus, the most important advancements in lighthouse technology over the years often have focused on the light itself.

The Fresnel lens, invented by a French scientist named Augustin Fresnel in 1822, quickly revolutionized lighthouses in Europe. The Fresnel lens looked like a glass beehive. A circular glass lens surrounded a light source at the center and prisms added to the top and bottom of the lens helped concentrate the light into a horizontal beam. A prism is a piece of glass cut with precise angles and plane faces, which reflects or refracts (bends) light waves. Fresnel lenses came in seven different sizes or “orders”—first, second, third, third-and-one-half, fourth, fifth and sixth—depending on the intensity of the light desired. Each lens was further classified as revolving or fixed. A revolving lens produced a flashing light as the lens rotated around the light source. A fixed lens produced a constant beam of light. Different flashes or “characteristics” helped mariners distinguish one lighthouse from another. The largest or first-order lens was almost 8 feet tall and more than 6 feet in diameter. It was intended for use in coastal lighthouses that needed to be visible from great distances. The smaller lenses (fourth, fifth, and sixth-orders) were used in lighthouses marking harbors or bays. A fourth-order lens was approximately 2 ½ feet tall and 1 ½ feet in diameter.

The United States was slower to adopt this new technology. At the time the Fresnel lens was invented all U.S. lighthouses were equipped with oil lamps in front of silver-plated pieces of copper that reflected the light. This system used vast quantities of oil and provided only a weak light. The Fresnel lens, on the other hand, captured and focused a much larger portion of the light emitted by lamps than did reflectors, and required less oil. In 1841, the first Fresnel lenses in the United States were placed in service in the original Navesink light towers. The federal government installed a fixed, first-order lens atop the south tower and a revolving, second-order lens atop the north tower. When the towers were rebuilt in 1862, the south tower’s first-order lens was moved to the new tower, while the north-tower’s lens was upgraded to a first-order.

By 1851, the industrial revolution had begun to transform America. Yet only two additional lighthouses had received Fresnel lenses. These were Sankaty Head in Massachusetts and Brandywine Shoal, an offshore lighthouse in the Delaware Bay. In 1852, the newly formed Lighthouse Board affirmed that “the lights at Navesink (two lenses) and the second order lens at Sankaty Head, Nantucket, are the best lights on the coast of the United States” and that they “are to be considered, as a general rule, equal to European lights of the same classes.” When comparing the lights at Navesink with the light at nearby Sandy Hook the report concluded that “the relative useful effect of the Navesink and Sandy Hook lights is in the proportion of 5.2 to 1; or, the Navesink lights are 5.2 times more powerful and effective than the Sandy Hook Light.”1 The success of the new lenses at Navesink convinced the Lighthouse Board to convert all outdated lighting equipment at existing lighthouses to Fresnel lenses but it would take more than a decade to do so. A fourth-order Fresnel lens was installed at Robbins Reef in 1855.

In 1875, Robbins Reef was selected as a location to conduct additional lighting experiments. It was chosen in part because it was located close to the federal Lighthouse Depot on Staten Island, Here the Lighthouse Board experimented with the use of kerosene in the lamps rather than the colza oil or lard oil being used at the time. Kerosene produced a more brilliant light than lard oil, which gave off a lot of smoke when burned. Successful tests convinced the Lighthouse Board to begin converting lamps over to kerosene in 1878 for lighthouses that contained fourth-order or smaller lenses. In 1883, a new revolving fourth-order lens was installed at the top of the new Robbins Reef lighthouse. The lens was illuminated by a kerosene lamp and kerosene was also tested in conjunction with the larger lens of Navesink. A kerosene lamp was first placed in Navesink’s north tower, where it was also successful, and the fuel soon replaced lard oil as the standard for the larger lenses found in coastal lighthouses. The following year, a kerosene lamp was placed in the south tower at Navesink.

The next significant technological event at Navesink occurred in 1898, when the Lighthouse Board purchased a new type of lens from the French Government called a “bivalve” Fresnel lens.It consisted of 386 separate lenses around a central bull’s eye lens. The bivalve lens was 9 feet in diameter and 5 feet high and resembled a giant clam shell. At the center of the lens was an electric lamp, which produced a superior light. After some indecision on the part of the Lighthouse Board about which lighthouse would receive the lens, the south Navesink tower became its destination. Upon installation, Navesink became the first coastal lighthouse in America to be powered by electricity. The Board thought that the importance of marking the entrance to New York Harbor warranted placing the lens here and the high elevation of the lighthouse contributed to the light’s visibility. Flashing once every five seconds for the duration of 1/10 of a second, it was visible for 22 miles at sea. The powerful lens made Navesink the brightest lighthouse in the United States and there was little danger of it being mistaken for another coastal light. Thus, the north tower light was no longer necessary and was reduced to backup status.

Other significant experiments conducted at Navesink were related to communication technology. In 1899, an Italian scientist and inventor named Guglielmo Marconi placed an antenna and receiving station at the Navesink Lighthouse to demonstrate his wireless telegraph. Marconi’s wireless telegraph sent a message in Morse code, which was transmitted via electromagnetic waves. The New York Herald newspaper had hired Marconi to bring his wireless telegraph to the United States and report on the 1899 America’s World Cup yacht races being held off the tip of Sandy Hook, New Jersey. The demonstration worked so well that Marconi expanded his American operation. He established the nation’s first commercial wireless telegraph station at Navesink capable of sending and receiving messages on a regular basis. Eventually Marconi’s ship-to-shore communications equipment would become standard on ocean-going vessels, improving the safety of maritime transportation. Marconi’s experiments led to the development of commercial wireless telegraph equipment, which became the forerunner of modern radio communications.

The United States Army also used Navesink as a test site for experimental electronics and detection devices. From July 30 to August 9, 1935, heat-seeking equipment known as thermopiles were used to track ships approaching New York Harbor. The Army Signal Corp was in the process of experimenting with various methods of doing this and needed a high vantage point to test their equipment. The unparalleled view from the hill of the Navesink Lighthouse provided that vantage point. The tests required the use of a powerful searchlight, so mariners were warned of its use. Four years later, in 1939, the Army Signal Corp was again at the lighthouse. This time they tested the effects of higher altitude on long-range radar sets. Once testing was completed all evidence of the top-secret radar equipment was removed.

Questions for Reading 2

1. What year was the Fresnel lens invented? By whom

2. Describe the appearance of Fresnel lenses. How did they work?

3. Using the classroom floor or wall, measure the height of a first-order and a fourth-order Fresnel lens. Why do you think Navesink Lighthouse received first- and second-order Fresnel lenses, while Robbins Reef received a fourth-order lens?

4.
What were some of the “firsts” at Navesink Lighthouse? What were some of the reasons Navesink and Robbins Reef were considered good places to conduct technological experiments?

Reading 2 was based on U.S. Light-House Establishment, Public Documents and Extracts from Reports and Papers Relating to Light-Houses, Light-Vessels, and Illuminating Apparatus, and to Beacons, Buoys, and Fog Signals, 1789-1871 (Washington, D.C.: GPO, 1871); U.S. Lighthouse Establishment, 1852 Lighthouse Board Report (Washington, D.C.: GPO, 1852); and “Navesink Light Station” (Monmouth County, New Jersey) National Historic Landmark Nomination Form.